The display device on a mobile device, such as the computer monitor, or the screen on the laptop or phone, consumes large amounts of power. For instance, in some devices, the display may consume between thirty to forty percent of the total power consumption at any particular point in time. Imagine the power wasted to energize a display when the device is not being actively used. Power mismanagement is amplified on mobile devices which have a finite amount of battery power.
Energy savings can be achieved by turning the display off when a user is not actively interacting with the device. Device interaction is detected by the presence of keyboard or mouse events, for instance. Conversely, device non-interaction is detected by the absence of keyboard or mouse events. In conventional systems, a rudimentary power management system is implemented that defines a single and static timeout period, after which the display of the device is turned off. In essence, the device is monitored for the display timeout period, and if no interaction with the device has occurred during the period, the display is then turned off.
A short and aggressive display timeout can provide large energy savings, but can irritate the user by causing frequent interruptions during periods of light activity. On the other hand, a large and conservative timeout, while causing less annoyance, provides fewer opportunities for energy savings.
The static timeout period is suitable for devices dedicated to a single purpose, such as work computers that operate within a well defined mode of operation on a continual basis. As such, usage of the device is consistent over time, and so a static timeout period on average provides the least amount of annoyance to the user.
However, for devices that operate within dynamically changing environments, the statically defined timeout period is insufficient for implementing a power management scheme. For instance, portable devices are used in various environments where the user places varying demand on the device. For instance, the user may at one time be at home and having the device plugged into an infinite power source, where power management of the device is not so critical. As such, a long timeout period that does not disturb the user would be appropriate. On the other hand, at another time the user may be traveling by air for a long stretch of time, in which power management of the device is very critical. If the timeout period is statically defined for home use of the device, that longer timeout period would be inappropriate for the user when traveling. That is, the user would quickly find out that the battery has drained because the display is constantly operating as if there were an infinite amount of power. Thus, even though the environment within which the device is being used is changing, the static timeout period has not changed with the environment.